Backflow preventer with vacuum breaker



March 6, 1962 J, C, BlsSLL 3,023,766

BCKFLOW PREVENTER WITH VACUUM BREAKER INVENTOB JACOB C. B/SSE/ L BY 7M# MVLW ATTORNEYS l 2 Sheets-Sheet 2 J. C. BISSELL BACKFLOW PREVENTER WITH VACUUM BREAKER March 6, 1962 Filed March 1o, 1958 INVENTog ATTORNEYS pull United States Patent O1 3,023,766 BACKFLOW PREVENTER WITH VACUUM BREAKER Jacob Cyril Bissell, 6310 14th St., Detroit 8, Mich. Filed Mar. 10, 1958, Ser. No. 720,241 3 Claims. (Cl. 137-218) The present invention relates to a device for preventing backllow in pressure-operated liquid supply lines and apparatus therefor.

One object of the invention is the provision of a backilow preventer which is positive in its action and which is especially effective in preventing back siphonage.

Another object of the invention is the provision of means for protecting a water supply and the like against backow contamination.

Still another object of the invention is to improve that class of backow preventers wherein valve means are responsive to liquid pressure.

Other objects of this invention will become more readily apparent from the following detailed description of the invention.

In general, the objects of the invention are achieved by means of a valve assembly actuated by pressure changes in the liquid supply line in which it is positioned. The valve assembly includes two separate simultaneously actuated valves spaced a short distance apart along the supply line to d'ene a breaker section and a third simultaneously operated relief valve for opening the section of line between the first and second valves to the outside atmosphere. In that preferred form of the invention illustrated in the drawings, the lfirst two valves are gate valves, although other valves could be substituted in less advantageous constructions. The third valve may be a simple valve of any known construction so long as it breaks any vacuum which might tend to cause back siphonage.

The gist of the invention is the automatic isolation of a line section and relief opening thereof upon a predetermined drop in the liquid supply ow pressure.

The invention will be better understood -by referring to the attached drawings in which:

FIG. l is a side elevational view showing a preferred form of the invention with some of the operative elements illustrated in dotted lines:

FIG. 2 is a View partly in section and partly in elevation taken along line 2-2 of FIG. 1; and

FIG. 3 is a sectional view of the relief valve shown in elevation in FIG. 2 and in dotted lines in FIG. 1.

In the form illustrated in the drawings, a backow preventer, as a unit, is placed in a water supply line adapted to operate in a predetermined pressure range. The same purpose could be accomplished with less facility by assembling separate parts into a liquid supply line.

This preferred form of the invention includes a housing or casing having an inlet 12 and an outlet 14 attached to water inlet line 16 and outlet line 18, respectively. A gate valve 22 is adapted to close inlet 12 and a gate valve 24 is adapted to close outlet 14. A relief valve indicated generally at 26 is adapted to open the middle of the casing to the air.

The purpose of the gate valves 22 and 24 is to form a double line closure isolating the interior of the casing to form what may be termed a breaker section 28. The purpose of the relief valve 26 is to break any vacuum formed in the breaker section 28 which might tend to cause back siphonage, and this is very effective when one of the gate valves gets stuck or fouled.

The three Valves are operated simultaneously by a single lever indicated generally at 30 and having a weighted end 32 and a free end 34.

A lever is mounted on shaft 36 for rotation therewith.

3,023,766 Patented Mar. 6, 1962 One` end of shaft 36 carries gate' valve 22 and the other end of the same shaft carries gate valve 24 so that lowering the weighted end 32 of lever 30 rotates shaft 36 and valves 22 and 24 to close inlet 12 and outlet 14. Conversely, raising weighted end 32 of lever 30 opens inlet 12 and outlet 14 in the same way.

The free end 34 of lever 30 carries an abutment means in the form of arm 38 which, in its uppermost position, engages an abutment means 39 at the rear of a shaft 40 of relief valve 26 to force the valve to the open dotted line position of FIG. 3. It will be seen that valve 26 includes, in addition to shaft 40, a valve head 42 mounted on the shaft and in a casing bore 44, and a spring 46 normally urging the valve head 42 to remain seated in the bore 44 in the closed position.

Shaft 40 extends through a sealed bore 45 at the rear of the casing to' a point well outside the casing and is provided with an abutment surface 39 adapted to be pressed by arm 38 of lever 30 as previously described to force valve head 42 out of bore 44 and open the breaker section to the atmosphere.

The length of the free end 34 of shaft 30 and the length `of arm 38 are so constructed that relief valve 26 will be opened just as gate valves 22 and 24 are finally closed by rotation of shaft 36.

The preferred means illustrated for actuating the operating lever 30 includes a pressure expansible assembly indicated generally at 50, and a Weight 100. The pressure expansible assembly includes a chamber 52 having rigid walls 54, a flexible diaphragm 5'6, a footed link 58 connected by sliding pin 55 and slot 57 at one end to the Weighted end 32 of lever 30 and in engagement at the footed end with the expansible diaphragm 56, and a pressure inlet 60. The pressure inlet 60 is provided with a conduit 62 leading to the liquid supply inlet 16 so that the pressure of the liquid supply is reected in chamber 52 to control the expansion of the diaphragm 56.

Suitable brackets 70 are provided for associating the pressure expansible assembly with casing 10.

Thus it will be seen that tne weight predetermines the pressure level at which the backflow preventer will be actuated. If the pressure in line 16 is sufficient to enable diaphragm 56 to support the Weight 100, the gate valves 22 and 24 will remain open and relief valve 26 will remain closed.

As soon as the pressure in line 16 becomes low enough that diaphragm 56 can no longer support Weight 100, the weight 100 will force weighted end 32 of lever 30 down, thereby turning shaft 36 and gate valves 22 and 24 to the closed position. This same ymotion raises free end 34 of lever 30 and just as the gate valves close, arm 38 hits abutment 39 to open relief valve 26. rl`he backdow preventer remains in this position until the pressure in line 16 rises to a level high enough to permit diaphragm 16 to be expanded to lift the weight 100 on lever 30 through link 50, whereupon normal operations resume automatically.

In actual tests, this device has proven extremely satisfactory and completely workable under a wide range of adverse conditions. In one test, in a water supply line designed to be operated at between 2() and 90 pounds per square inch, a inch backtlow preventer constructed in accordance with the invention with a 20 pound weight 100 was used to effect full closure at l2 pounds per square inch. Back siphonage was attempted by use of vacuum of up to 25 inches of mercury in the line 16, but the device continued to perform satisfactorily. When gate valve 22 was purposely fouled with 0.054 inch copper wire, back siphonage was only a vertical distance of 4 feet under 22 inches of mercury. After a short period `of time, the gate valve cut through the wire and back siphonage was absolutely stopped.

In such installations it is desirable to provide a container for liquid escaping through relief valve 26.

Thus it will be seen that the backtlow preventer of the present invention is highly resistant to fouling, positive in action and practically fool proof. Certain modications of the preferred form of the invention may be made by those skilled in the art without departing from the scope of the invention as defined in the following claims.

I claim:

l. A backow preventer comprising a casing having an inlet and outlet connected in a liquid supply line, two gate valves for opening and closing said inlet and outlet, respectively, a relief valve for the casing, means operatively associated With said casing for operating said valves simultaneously and alternately to open said relief valve as it closes the other valves and to close the relief valve as it opens the other valves, and pressure responsive means in communication with the liquid supply line and operatively connected with said valve-operating means to close the inlet and outlet valves and open the relief valve when the pressure in said line falls below a predetermined level, said valve-operating means including a member for operating said gate valves and a lever mounted intermediate its ends on said member for moving same, one end of said lever operating push means for opening said relief valve and the other end of said lever connected with said actu-ating means.

2. A bacltlow preventer comprising a casing having an inlet and outletV connected in a liquid supply line, two gate valves for vopening and closing said inlet and outlet, respectively, a relief valve for the casing, means operatively associated with said casing for operating said valves simultaneously and alternately to open said relief valve as it closes the other valves and to close the relief valve as it opens the other valves, and pressure responsive means in communication with the liquid supply line and operatively connected with said valve-operating means to close the inlet and outlet valves and open the relief vvalve when the pressure in said line falls below a predetermined level, said valve operating means including a single shaft for operating said gate valves and a lever mounted intermediate its ends on said shaft for rotating same, one end of said lever operating push means for opening said relief valve and the other end of said lever connected with said actuating means.

3. A device as set forth in claim 2 wherein said actuating means includes a removable and replaceable weight on the actuated end of said lever, said pressure responsive means including a pressure eXpansible member attached to the actuated end of said lever, and said weight is opposing expansion of said expansible member whereby different weights may be used at dilferent times to predetermine the pressure at which said valves Will be opened and closed.

References Cited in the tile of this patent UNITED STATES PATENTS 1,688,586 Lewis Oct. 23, 1928 1,826,941 La Mont Oct. 13, 1931 1,905,625 Pagen Apr. 25, 1933 2,620,816 Griswold Dec. 9, 1952 2,638,124 Nickerson May 12, 1953 2,646,064 Colton Tuly 2l, 1953 

